This is a competing continuation to further localize and identify a gene for early onset primary torsion dystonia (PTD). The gene under study is DYT6, one of several genes that can cause this disease. 1)They plan to examine 30 families in which 3 or more members are affected with PTD. They will also examine 50 simplex or multiplex Mennonite PTD families. 2) They will carry out a series of genetic tests to further elucidate the genetic defect in these families. 3) Families displaying linkage or linkage disequilibrium will be used to further localize and characterize these genes by positional cloning. Families excluded from linkage with identified PTD loci will be analyzed by linkage analysis in a genome search. Once other PTD loci are identified, further localization by fine scale mapping will be performed and linkage disequilibrium will be sought. Clinical features due to different PTD loci will be determined and explanations for the variable expression and reduced penetrance of PTD genes will be investigated.